Beginning Metaphysics III: Introduction to Essence and Existence

Suppose you walk outside one day and suddenly come across some strange object you’ve never encountered before. You’re first thought will most likely be, “what in the world is that?” This question of what something is, as simple as it may seem, is extremely profound. For as soon as we ask what something is, as soon as we pose the question “what is it?” or “what is X”, we have embarked upon a metaphysical journey.

So what’s so special about the question of “what is it”? Suppose that, after asking the question about the strange object in front of you, a friend who’s with you responds “That is a giraffe”. Disregarding the justified curiosity concerning what in the world a giraffe is doing outside your home, we must admit that the answer given us is intelligible. This is not to say that we necessarily fully comprehend the question. After all, perhaps we do not have any idea of what a giraffe is in the first place. But the answer itself, and its structure, is intelligible. We understand what meaning the statement is trying to convey, even if we do not know exactly what it is it’s identifying. But suppose instead that when we come across the object and ask “what is it?” our friend merely responds “it is”. We might then say, “Yes, I know that it is, since I can see it, but I want to know what it is.” Hopefully the friend will then proceed to identify the object. But suppose he does not. Suppose he then just says, “Is”. And suppose that after repeatedly asking him to clarify, he merely continues to obnoxiously repeat that same terse statement: “Is.” At this point, we might very well think that our friend has gone mad. It’s not that his statement conveys no meaning whatsoever; the short word “is” is, after all, extraordinarily replete with philosophical significance (as Bill Clinton of all people wittily pointed out). It’s that the meaning, in this instance, is unintelligible, especially in relation to our question. It simply makes no sense to assert that “is” without making some sort of reference to what it is that is.

But this is actually quite revealing about the nature of reality itself. Our statement “that is a giraffe” can be simplified to “that giraffe is”, which is of the structure “that which is”. In the previous post, we discussed briefly what it means to say that something exists in the first place. At the beginning of his De Ente et Essentia St. Thomas Aquinas comments that perhaps the very first thing we know, at all, is “being”, or that things exist, that something exists. But notice, again, that we cannot intelligibly talk about existence except in terms of the “that which is” structure. Our language reflects this at its most fundamental level: Any sentence, in order to actually be a sentence, must consist of at least a subject and a verb. To utter “Cake” is not to make a comprehensible sentence, since it tells us nothing about that which is asserted, not even if it actually exists. And to utter “Is”, again, or “Runs” or “Throws”, tells us even less. The first thing we know is that something exists, that being is, a being is that which is. But, as philosopher W. Norris Clarke points out, this structure contains “two irreducible yet inseparable aspects: the is of actual existence and the that which, the subject which exists or has existence” [1]. In other words, in order to speak intelligibly about reality, we must recognize both essence and existence. This is the doctrine upon which the entire Thomistic metaphysical system is constructed.

To present St. Thomas’s metaphysical system, one could possibly begin from basically three different starting points: the essence/existence principle, the act/potency principle, or the matter/form principle. Some choose to begin with act and potency, since, in a way, all three principles are actually different manifestations of the act/potency principle; or, at least, all can be explicable in terms of act and potency. But even though the act/potency principle might be the most comprehensive of the the three, the most metaphysically fundamental is certainly the essence/existence distinction, and so it is here that we shall begin, as St. Thomas himself does.

But notice that at the start we have a slight problem, both linguistic and metaphysical. The verb “is” is a form of the verb to be, or, in Latin, esseEsse in all its forms designates be-ing. But things can “be” in different sense, as is evident by our different ways of speaking. One might say: “That man is tall”, in which case the “is” references some really existing attribute of “that man”. But one might also say: “A giraffe is a mammal”. Notice that in this usage, the “is” functions more as defining/extrapolating on the definition of “giraffe”. The giraffe may or may not actually exist. So St. Thomas writes:

“We should notice, therefore, that the word “being,” taken without qualifiers, has two uses, as the Philosopher says in the fifth book of the Metaphysics. (1) In one way, it is used apropos of what is divided into the ten genera; (2) in another way, it is used to signify the truth of propositions. The difference between the two is that in the second way everything about which we can form an affirmative proposition can be called a being, even though it posits nothing in reality. It is in this way that privations and negations are called beings; for we say that affirmation is opposed to negation, and that blindness is in the eye. In the first way, however, only what posits something in reality can be called a being. In the first way, therefore, blindness and the like are not beings” [2].

So, in the first sense, esse asserts real, actual existence in some aspect. In the second sense, esse “signifies the truth of propositions” or, as Clarke puts it, “functions merely as a copula to join together a subject and a predicate without committing itself to the reality of either” [3]. This distinction is important, as St.Thomas points out, because in the second sense, anything about which we can “form an affirmative proposition can be called a being, even though it posits nothing in reality”. So we could say “bachelors are unmarried men”, and this use of esse would be true enough, but does not tell us about the actual reality of the subject or the predicate; it merely relates the two. It does not refer to any specific, actual bachelor, just to a general idea of bachelors. For our purposes then, we will be concerned mainly with the first sense of esse.

But this has some significant implications. Recall our initial example: You walk outside, see some strange object, and ask “What is it?” Now imagine a different situation. You’re eating a meal with some friends and they begin a conversation about what a unicorn is. At some point, you stop them and ask, “Are there unicorns?” by which you mean, “Do unicorns actually exist?” As George P. Klubertanz points out, “It is quite clear that the questions, ‘What is it?’ and ‘Is it?’ are two quite different questions” [4]. From this it follows, as shall be demonstrated below, that what something is, is different from that it is; or, as we shall say it, essence is distinct from existence. This follows from everything that has been said previously.

Aquinas writes:

“Now, every essence or quiddity can be understood without anything being understood about its existence. For I can understand what a man is, or what a phoenix is, and yet not know whether they have existence in the real world. It is clear, therefore, that existence is other than essence or quiddity, unless perhaps there exists a thing whose quiddity is its existence” [5].

There are many ways one could go about defending this principle of the distinction between essence and existence, and not all of them will be presented here. Instead, in this post I just want to lay out some general lines of thought that indicate/point to/offer support for the principle. As the series goes on, I’ll expand these more fully.

The first reason to hold to the essence/existence distinction has to do with what is known as “the problem of the one and the many”, a problem which is “the ultimate paradox of being and the deepest and most fundamental problem of all metaphysics, of every intellectual effort to achieve a total, unified vision of all reality” [6]. It is the problem that drove in many ways the philosophical inquiry of ancients such as Parmenides, Plato, and Aristotle, and it has continued to be a central issue in philosophy since then. Clarke offers a short summary of the problem:

“How all beings, compared with each other, are at once many and diverse, yet somehow share in the common attribute of actual existence that joins them in one great all-embracing community of existents that we call ‘the real order,’ or simply ‘reality.’ Thus the totality of the real is somehow both one and many. How can this be? How must reality be structured in order to remain at once both many and diverse yet sharing in a common unity?” [7].

And then:

“As soon as I attempt to take a synoptic view of all beings as beings, to compare all beings together . . . I discover that I am obliged to affirm two apparently opposing propositions about each one of these beings. I am compelled to affirm that every single real being, compared to every other, is at once similar to every other, because each one is, exists, is real; and yet dissimilar to every other, because each one is precisely this being and not that one . . . Both of these basic attributes must be maintained, if I am to do justice to my experience and to the common bond underlying all expressions of my experience” [8].

In other words, we notice immediately in our experience not just that something exist, but that many different things exist, many different particular beings, many different types of beings, etc. We know that they are similar, at least insofar as they actually exist; but we also recognize that they are distinct, unique, separate from other beings. We distinguish giraffes from elephants from trees from mountains from molecules from atoms from electrons from protons, etc. And yet they all are, they all exist, they all have unity, they all are a part of a whole reality. How is this so?

There are, historically, a number of different approaches that different philosophers/schools of thought have taken in trying to come to terms with this fact. As Clarke points out, our options are either to affirm both the multiplicity and the unity of beings, in which case we would need to offer some explanation thereof; or we can deny one aspect “as mere appearance, illusion, or projection of our minds” [9]. Parmenides, for instance, as we’ve discussed many times, denied the reality of any multiplicity in being. Being is all that exists, and it is absolutely one. This is radical monism The other extreme would be radical pluralism, which denies any unity in being. In between are a variety of other positions, including those of Plato, Aristotle, and Aquinas.

So how exactly does St. Thomas attempt to solve the problem of unity and multiplicity? By positing that there are a multiplicity of essences that diversely “participate in” being, the unity of existing. This unity of being, as we explained in the previous post, is analogous, but it is still real. In other words, the similarity between a tree and a bird is that they both have existence, even if the way in which they have existence, due to their distinct essences, is different. Hence, to affirm both multiplicity and unity, we must affirm the reality of both essence and existence. Everything that exists must have both an essence, a what it is, and an act of existing, a that it is.

And these must also be distinct, not identical to each other, for the following reasons:

1. As indicated earlier, our knowledge of what something is does not tell us whether or not it actually exists. We can have a knowledge of the essence/nature of humanity, and this knowledge will tell us absolutely nothing about whether or not any particular human beings really exist. After all, it could be the case that in a few million years the human species has died off. At this point, the essence of humanity will still be what it is, by definition; but no human beings will actually exist. We can know what dinosaurs were even while knowing that no dinosaurs still exist. Furthermore, this is even true of things which have never existed. We can speak, for instance, of the essences of unicorns and dragons and phoenixes, but knowing what these things are tells us nothing about whether they are. If their essence and act of existing were identical, knowing the essence would tell us whether the thing in question actually exists.

2. If the essence and existence were identical, than that thing would always exist. The essence of a thing is its nature, what determines the necessary, immutable, common attributes of all particular instances of that type of thing. For example, the essence of a triangle includes having three sides. By definition, since the essence of a triangle includes having three sides, any and every triangle will always have three sides. So if any essence included “existence”, then that essence would always, by definition, have existence; and hence would always exist. But the things of our experience are most definitely not like this.

3. If essence and existence were identical, then there could be no multiplicity of essences. Essence designates a common nature. All individual human beings share the common nature of “humanity”. The common essence must lack existence as intrinsic to itself, since it must be allowed to be united to individual acts of existence in order to account for the many different beings of our experience. But if an essence had an act of existing as intrinsic to it, then it would just exist as itself, as one. But this, again, does not fit our experience of many different beings sharing one essence. Hence essence and existence must be distinct.

This, admittedly, has been an extremely brief and surface level introduction to Aquinas’s principle of essence/existence distinction. This is somewhat intentional: I’m anticipating several responses to be made, and objections to be raised, and so I’ve purposefully left room for expansion/extrapolation in future posts. By no means is this a comprehensive, in depth, or philosophically sophisticated defense of the doctrine; it is rather meant as just a summary of the general idea, which I will hopefully proceed to delve into more in the coming months.



[1]. See Clarke, W. Norris. The One and the Many: A Contemporary Thomistic Metaphysics. Notre Dame: University of Notre Dame Press, 2001. Print, 25-26.

[2]. Aquinas, Thomas. De Ente et Essentia. Translated as Aquinas on Being and Essence:
A Translation and Interpretation. 1965. Adapted and html-edited by Joseph Kenny, O.P. <>.

[3]. Clarke. The One and the Many. 25.

[4]. Klubertanz, George P. Introduction to the Philosophy of Being. 2nd edition. Eugene: Wipf and Stock Publishers, 2005. Print, 109.

[5]. Aquinas. De Ente et Essentia.

[6]. Clarke. The One and the Many. 72.

[7]. Ibid.

[8]. Ibid. 73.

[9]. Ibid. 74.

Header Image: Vincent van Gogh [Public domain], via Wikimedia Commons <>.


2 thoughts on “Beginning Metaphysics III: Introduction to Essence and Existence

  1. Even the word “is” is tricky. In a sense nothing “is” exactly the same as something else because for every two things that exist they each exist in their own unique time and place, and everything is in motion, ever changing, and even matter and energy exist as matter-energy, not totally distinct from one another.

    He use of “is” often holds one back from recognizing everything is in process when in fact everything has a history requiring multitudes of words to describes its development in time and place, from the development of stars and planets to the development of species including the human species.

    Even when someone says they “are” a Christian or atheist, no single word or label truly tells you all that that person “is,” because it takes a multitude of words to describe a person in all their aspects related to everything to which they are related as a person.

    Christians or atheists may also have wavering thoughts at different times concerning what they supposedly “are,” or even undergo a radical change of beliefs.

    So “is” implies a static understanding of nature and even of individuals or groups, but nature and people are dynamic. Some have challenged others to try speaking without using the word “is,” or labeling others using singular terms. They thought it could help us find more common ground. In science we examine nature and how it works, what the processes of nature are, because life is an activity, a verb not a noun.

    Aristotelian “is-ness” compared to a more operational language, a language of dynamic interactions can be read about in this piece, let me know what you think of it

    Sent from my iPad


    • Sorry for taking so long to respond. I’ve glanced over the article you linked, but won’t have a chance to analyze it fully and respond in depth for a while. For now, I’d just say that I don’t think an Aristotelian or Thomistic understanding of “is” and essence requires a strictly “static” understanding of reality as opposed to dynamic. In fact, as I pointed out in the previous article in this series, Aquinas very much saw “is-ness” and existence as entirely an activity, an action. The limit comes from the essences of things. The facts that things change, and perhaps are always undergoing some sort of change, is not indicative of a lack of an essential nature. Nor is the fact that there are many different factors that go into defining an individual. Nor is the fact that there are many different “individuals” that might fit under some common essence. All of these things are for the most part admitted by Aristotelians and Thomists. But I will try to read the article in depth and get back to you as soon as I can (may be a week or more).


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